1. Field of the Invention
The invention is directed to a device for the suspension of a hollow-section rail in an overhead or suspension crane which opens downward.
2. Description of the Related Art
A prior art hollow-section rail which opens downward for a suspended rail system is disclosed in the brochure titled "Kranbaukasten KBK (KBK Crane Construction Kits)", for a crane construction kit manufactured by Mannesmann Demag Fordertechnik AG. A lifting device is movable in the longitLudinal direction of the suspended rail system by trolley rails. The rail is suspended in pendulum fashion so as to be swivelable, at a carrying apparatus or a transverse girder by vertically arranged, elongate girders or traction elements, wherein the lower ends of the traction elements are fastened to the rail and the upper ends are fastened to the carrying apparatus or transverse girder. The pendulum type suspension ensures that the suspension path automatically adjusts to the state of equilibrium. The state of equilibrium is the state in which there are no horizontally acting forces and all forces are directed vertically downward. The pendulum type suspension is ensured in that the ends of the girders are provided with ball heads which are articulated in matching ball sockets at the rail or at the carrying apparatus. In the case of pendulum type suspension, shock-like loading of the rails in particular is transformed into vibrational energy, the rails proceed back to their initial position again in the form of damped oscillations.
The pendulum type suspension described above is not suitable for a suspension crane, especially with a laterally projecting boom, because upwardly directed vertical forces are not absorbed.
Consequently, as an alterinative solution in a suspension crane with a laterally projecting boom, only a rigid suspension of the rails is taken into consideration. The rigid suspension has the disadvantage that pulse peaks occurring during shocks may destroy or damage the suspension path and ceiling construction because, in these cases, besides the forces that are favorably absorbed by the suspension system, short-term horizontal forces with very large amplitudes also occur. But horizontal forces also occur during normal operation of the suspension crane, specifically because of bending or sagging of the rails between the individual suspension points. These horizontal forces during normal operation likewise represent an intensive loading of the suspension path which manifests itself over the course of time by increased wear.